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Slide Rules

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Slide rules were sometimes distinctive by the materials from which they were made. Early rules were often made from boxwood and other woods. By the late 19th century, German manufacturers and Keuffel & Esser of New York City had not only switched to the more uniform and durable mahogany but were also coating the wood with early forms of plastic (celluloid). Around the turn of the 20th century, Japanese firms used bamboo, which did not expand and shrink as much as wood, thus reducing errors in the results of calculations. Later, Pickett slide rules were notable for their aluminum construction and proprietary yellow color. Although the rules tended to be less affordable and popular than wooden rules, manufacturers have used brass and other metals throughout the history of slide rules. Plastic and paper became increasingly widespread for inexpensive rules in the 20th century.

The back has charts for converting between cubic meters and cubic feet; gallons and liters; miles and kilometers; inches and centimeters; and fractional inches and millimeters. A table of miscellaneous conversions appears in the center of the back.

Around 1960 a former employee of the Perry Graf Corporation (see 1979.3074.03) established Datalizer in Addison, a Chicago suburb. The company made this promotional rule during a time of considerable interest in adopting the metric system in the United States. The New York Daily News used the "picture newspaper" slogan between 1920 and 1991.

This ten-inch, one-sided plastic rule has a yellow base, a white slide, and a transparent indicator. Identical logarithmic scales are on the top and the bottom of the base. Both sides of the slide are marked with pairs of metric and conventional units. On one side, the user can read off conversions between: inches and centimeters; meters and feet; meters and yards; miles and kilometers; square inches and square centimeters; square meters and square feet (times ten); square meters and square yards; and square miles and square kilometers. The other side of the slide permits readings of cubic inches and cubic centimeters (times ten); cubic meters and cubic feet (times ten); cubic meters and cubic yards; liters and quarts; ounces and grams (times ten); kilograms and pounds; metric tons and short tons; and gallons and liters.

Sterling Plastics, a 20th-century manufacturer of drawing instruments for schools, was purchased by Borden Chemical in 1970. Since Sterling stopped making slide rules in 1972, this example of model number 651 was probably one of the last rules produced by the company. The five braces holding together the base of the instrument are also consistent with this date; early Sterling slide rules had only two braces. For instructions, see 1990.0689.03. For a Sterling slide rule with standard scales, see 1988.0807.01.

Around 1970 many American companies and government agencies encouraged Americans to adopt the metric system. Regal Beloit of Wisconsin and other manufacturers of cutting tools and gear boxes adopted the units of measure and distributed devices like this one to assist in their use.

The one-sided white cardboard rule is printed in orange and black and has eight windows. Two logarithmic scales on the slide are viewed through four of the windows so that the user can convert between yards or feet and meters; centimeters and inches; pounds and kilograms; and tons and metric tons. Two more logarithmic scales on the slide permit conversions between square yards and square meters; square centimeters and square inches; cubic yards and cubic meters; and liters and imperial gallons or U.S. gallons. Below the windows is a scale for converting between Celsius and Fahrenheit temperatures. The rule is marked: REGAL BELOIT. It is also marked metric/inch (/) CONVERTER. It is also marked SWANI PUBLISHING COMPANY (/) P.O. Box 284 • Roscoe, Illinois 61073 (/) 815 / 389-3065.

This one-sided five-inch white plastic rule has a plastic indicator attached as a bracket (i.e., there is no back). The base has K, A, D, and L scales, with B, CI, and C scales on the slide. The left end of the slide is marked: MODEL 61, and the right side has the Pickett triangular logo in white, which was chiefly used between 1950 and 1958. The number 38 is printed above the logo.

The rule slides into a black synthetic leather stitched case, which fits in an orange and black paper box. A Pickett triangular logo with block print and inside a circle appears on the box. This form of logo was used between 1962 and 1964. The logo and the plastic material used in the rule suggest the instrument was made in the 1960s.

The ends of the box are marked: PLASTIC TRAINER SLIDE RULE; NO. 61 (/) $1.95; FINEST QUALITY ENGRAVED (/) 5" SLIDE RULE. The top and bottom of the box describe the instrument as a STUDENT SLIDE RULE. It came with a pamphlet, "How to Use Basic Slide Rules in 3 Easy Steps" (1991.0445.02.01). Students were permitted to trade this rule in toward the purchase of a Pickett all-metal rule.

Argentine-born electrical and mechanical engineer Richard R. Lombardi used this slide rule and donated it to the Smithsonian. A price tag on the box and a receipt for the object indicates he paid $1.56; the receipt is dated 1971, although the trade-in certificate also included with the rule expired in 1966. Company marks on the pamphlet indicate it was printed after 1964.

This plastic circular slide rule has a white base, with three concentric logarithmic scales, all numbered from 1 to 50. The outer scale is labeled “SHOW (3rd)”; each unit has six subdivisions. The middle scale is labeled “PLACE (2nd)”; each unit has three subdivisions. The innermost scale is labeled “RACES WON”; units are not subdivided. There is a clear plastic hairline indicator.

A smaller gold disc lies atop the white one. It is pivoted at the center and has a logarithmic scale, running from 1 to 95 and marked: TOTAL RACES ENTERED. Two more logarithmic scales are visible through a window in the gold disc. These provide the total purses of the races the animal had entered and, finally, the performance-class factor rating. According to the donor, if F=number of first place finishes of a horse, S=number of seconds, T = number of thirds, R = number of races entered, and M= the total money won, the scale calculates the number [[100F + 33.333S + 16.666T]/R] + 1.12 M.

The gold disc is marked: K2 (/) PERFORMANCE/CLASS CALCULATOR (/) COPYRIGHT 1972 K2 PUBLISHING CORP. Accompanying the calculator are a paper instruction booklet, a sheet of paper giving the formula calculated by the machine, and a computer printout showing a similar calculation. The 20-page booklet was also copyrighted in 1972 and indicates the method can be used for thoroughbred, harness, and greyhound racing. K2 Publishing Corporation was located at 475 Northern Blvd., Great Neck, N.Y., where an office building was built in 1967.

Everything is stored in a black plastic case with a clear plastic front. Another slide rule for handicapping horse races is 1998.3050.02.

This rectangular white plastic slide rule has scales for sprint times from 5 to 7 furlongs; two columns for use with the average pace method for handicapping horse races; three columns for use with the highlight pace time method of handicapping; and scales for route times from 1 to 1-1/4 miles. This outer folder is marked: Ray Taulbot's Pace Calculator (/) WITH AMER-VAR; Published by (/) AMERICAN (/) TURF MONTHLY (/) 505 EIGHTH AVENUE (/) New York, N.Y. 10018; PRINTED IN U.S.A. COPYRIGHT — 1979 Amerpub Company.

Ray Taulbot (1895–1969) was the longtime managing editor of American Turf Monthly, a magazine for horse racing enthusiasts published by the Amerpub Company. He is credited with several innovations in handicapping races, particularly by rating a horse in comparison to the overall pace of a race. He believed horses must be judged by their own speed and by how close they were to the winner. A chart on the back of the calculator allowed bettors to combine the results of the Pace Calculator with the Amer-Var rating, which took into account the horse's age, the length of the race, the amount of the purse, the time of year, and the type of race. Taulbot's methods dated at least to the 1960s, but this device was made in 1979. American Turf Monthly continues to reprint Taulbot's articles.

For other devices made by Bastian Brothers, see 1987.0183.01 and 1988.0323.03.

This display of steps in the manufacture of slide rules also demonstrates the capability of dividing engines. It may have been assembled by Keuffel & Esser executives when the company donated two of its early 20th-century linear dividing engines (MA*335265 and MA*335266) to the Smithsonian in March 1971. The exhibit consists of a large dark green pegboard, to which slide rule components are fastened with wires and labels are attached with tacks.

The left panel displays the raw materials of slide rule manufacture: a rough mahogany slab, a planed mahogany slab, white xylonite (celluloid) to face the front and back of the wood, and a toothplaned mahogany slab. Each slab is approximately two feet long.

The middle panel shows the xylonite glued to a toothplaned mahogany slab, which is then depicted as cut in half to make two ten-inch slide rule forms. The forms are cut lengthwise in thirds, and then the edges are grooved so that the middle part slides between the two parts of the base. Next, a blank slide rule is machine divided.

The right panel displays slide rules that have been numbered and blackened, numbered and reddened, and ready to be assembled with L-shaped metal end pieces and screws. The assembled slide rule has been removed. Another example with front and back views of a completed model 4081-3, Log Log Duplex Decitrig, slide rule is missing the slide in the back view. Finally, the parts of an indicator are mounted on a card: two pieces of glass, two pieces of metal frame, one of the two plastic edges, and four screws. Compare the completed example to MA*318482, MA*334387, and 1990.0687.01.